Archivi tag: solar system

The Formation of the Solar System II

Although the solar system formed more than 4.5 Gyr ago there still exist a number of indicators to the conditions at the time of its formation. Meteorites, the composition of the Kuiper belt and even today’ s properties of the solar system planets give clues to the solar system’s early history. However, there is an ongoing debate on how to interpret these properties. Continua a leggere The Formation of the Solar System II

Revolution in Astronomy with ALMA

The Atacama Large Millimeter/submillimeter Array (ALMA) has been producing a growing number of impressive and scientifically compelling results as the most powerful mm/submm interferometer in the world. Held in central Tokyo, the aim of this four day conference is to highlight the most recent science results from ALMA obtained during the first three years of science operations, and to motivate future collaboration among researchers around the world. Continua a leggere Revolution in Astronomy with ALMA

The X-ray Universe

The XMM-Newton Science Operations Centre is organising a major astrophysical symposium from Monday 16th to Thursday 19th of June 2014 in Dublin, Ireland. The symposium is the fourth international meeting in the series “The X-ray Universe”. The intention is to gather a general collection of research in high energy astrophysics. The symposium will provide a showcase for results, discoveries and expectations from current and future X-ray missions. Continua a leggere The X-ray Universe

Ganymede might have ice and oceans like a ‘club sandwich’

Image of Ganymede’s anti-Jovian hemisphere taken by the Galileo probe. Lighter surfaces, such as in recent impacts, grooved terrain and the whitish north polar cap at upper right, are enriched in water ice. Credit: NASA

The largest moon in our Solar System, a companion to Jupiter named Ganymede, might have ice and oceans stacked up in several layers like a club sandwich, according to new NASA-funded research that models the moon’s makeup. Previously, the moon was thought to harbor a thick ocean sandwiched between just two layers of ice, one on top and one on bottom.

More at JPL: Ganymede May Harbor ‘Club Sandwich’ of Oceans and Ice

arXiv: A Passive Probe for Subsurface Oceans and Liquid Water in Jupiter’s Icy Moons

Video from

NASA Jet Propulsion Laboratory California Institute of Technology

Beta Pictoris b, measured the rotation rate of the exoplanet

Artist’s impression of the planet Beta Pictoris b. Credit: ESO

Observations from ESO’s Very Large Telescope (VLT) have, for the first time, determined the rotation rate of an exoplanet. Beta Pictoris b has been found to have a day that lasts only eight hours. This is much quicker than any planet in the Solar System, its equator is moving at almost 100.000 kilometres per hour. This new result extends the relation between mass and rotation seen in the Solar System to exoplanets. Similar techniques will allow astronomers to map exoplanets in detail in the future with the European Extremely Large Telescope (E-ELT).

More at ESO: Length of Exoplanet Day Measured for First Time

arXiv: The fast spin-rotation of a young extrasolar planet

Discovered a close neighbor of the Sun

This image is an artist’s conception of the brown dwarf WISE J085510.83-071442.5. The Sun is the bright star directly to the right of the brown dwarf. Credit: Robert Hurt/JPL, Janella Williams/Penn State University.

A “brown dwarf” star that appears to be the coldest of its kind — as frosty as Earth’s North Pole — has been discovered by a Penn State University astronomer using NASA’s Wide-field Infrared Survey Explorer (WISE) and Spitzer Space Telescopes. Images from the space telescopes also pinpointed the object’s distance at 7.2 light-years away, making it the fourth closest system to our Sun.

More at Penn State: Star Is Discovered To Be a Close Neighbor of the Sun and the Coldest of Its Kind

Science with the Atacama Pathfinder Experiment

After the success of the 2012 Ringberg meeting on APEX science where about 70 participants discussed exciting APEX science ranging from our Solar System to distant galaxies in the Early Universe, time is ripe to review what has been accomplished since then and to look into science opportunities for the next years. Since its inauguration in 2005, the Atacama Pathfinder Experiment (APEX) 12m submillimeter telescope has significantly contributed to a wide variety of submillimeter astronomy science areas, ranging from the discoveries of new molecules to large and deep imaging of the submillimeter sky. Among the partners the extension of APEX operations to 2017 and beyond is being prepared and new instruments are on their way and in the planning, including new wide-field bolometer cameras and new heterodyne instruments highly complementary to ALMA. While Herschel ran out of Helium, the work on its archival data benefits strongly from complementary APEX observations. SOFIA is collecting first exciting results where again lower frequency APEX studies needs to be added. With ALMA ramping up, we see already how important APEX is as a pathfinder for high angular resolution studies.

The conference venue Ringberg Castle will provide a unique setting for in depth discussions on current and future science with APEX. In particular, sessions on new scientific results, on synergies with other observatories and on APEX beyond 2015 are envisioned.

LSST@Europe: The Path to Science

The Large Synoptic Survey Telescope (LSST) project is now entering an exciting phase, moving towards the start of federal construction expected in 2014. With first light planned for 2019 and science operations to commence in 2021, it is now timely to consider the scientific opportunities of LSST in the era of major new European facilities, especially wide-field missions such as Gaia, eRosita and Euclid, and flagship ground based facilities such as ESO’s E-ELT.

This first LSST science meeting in Europe will bring together LSST scientists and European scientists involved in, or interested in, taking LSST forward. This will allow for discourse as to current key science, the role of LSST, and the role of European expertise and facilities in partnership with LSST, in driving forward the next astronomical science revolution into the 2020’s. The meeting will provide an opportunity to review the current status of the LSST, and the key science programmes which are underpinning its development. The conference will include presentations identifying current science challenges where a combination of LSST and leading new European facilities and expertise will result in major leaps in understanding. These topics will range from studies of our Solar System and the Milky Way, to the Universe at the largest scales.

All the light in the Universe since the Big Bang

Vi siete mai chiesti quanta luce è stata emessa da tutte le galassie da quando è nato l’Universo? Pensate un attimo a ciascun fotone di qualsiasi lunghezza d’onda, dall’ultravioletto all’infrarosso, che sta viaggiano ancora nello spazio fino a raggiungere i nostri rivelatori. Se riuscissimo a misurare in maniera accurata il numero e l’energia di tutti i fotoni, non solo quelli dei nostri giorni ma anche quelli più antichi, potremmo ricavare indizi fondamentali sulla natura e l’evoluzione dell’Universo e comprendere come le galassie più antiche siano differenti rispetto a quelle che vediamo oggi.

That bath of ancient and young photons suffusing the Universe today is called the extragalactic background light (EBL). An accurate measurement of the EBL is as fundamental to cosmology as measuring the heat radiation left over from the Big Bang, the cosmic microwave background, at radio wavelengths. A new paper, called “Detection of the Cosmic γ-Ray Horizon from Multiwavelength Observations of Blazars”, by Alberto Dominguez at University of California at Riverside and six coauthors, based on observations spanning wavelengths from radio waves to very energetic gamma rays, obtained from several NASA spacecraft and several ground-based telescopes, describes the best measurement yet of the evolution of the EBL over the past 5 billion years. Directly measuring the EBL by collecting its photons with a telescope, however, poses towering technical challenges, harder than trying to see the dim band of the Milky Way spanning the heavens at night from midtown Manhattan. Earth is inside a very bright galaxy with billions of stars and glowing gas. Indeed, Earth is inside a very bright Solar System: sunlight scattered by all the dust in the plane of Earth’s orbit creates the zodiacal light radiating across the optical spectrum down to long-wavelength infrared. Therefore ground-based and space-based telescopes have not succeeded in reliably measuring the EBL directly. So, astrophysicists developed an ingenious work-around method: measuring the EBL indirectly through measuring the attenuation of, that is, the absorption of, very high energy gamma rays from distant blazars. Blazars are supermassive black holes in the centers of galaxies with brilliant jets directly pointed at us like a flashlight beam. Not all the high-energy gamma rays emitted by a blazar, however, make it all the way across billions of light-years to Earth; some strike a hapless EBL photon along the way. When a high-energy gamma ray photon from a blazar hits a much lower energy EBL photon, both are annihilated and produce two different particles: an electron and its antiparticle, a positron, which fly off into space and are never heard from again. Different energies of the highest-energy gamma rays are waylaid by different energies of EBL photons. Thus, measuring how much gamma rays of different energies are attenuated or weakened from blazars at different distances from Earth indirectly gives a measurement of how many EBL photons of different wavelengths exist along the line of sight from blazar to Earth over those different distances. Observations of blazars by NASA’s Fermi Gamma Ray Telescope spacecraft for the first time detected that gamma rays from distant blazars are indeed attenuated more than gamma rays from nearby blazars, a result announced on November 30, 2012, in a paper published in Science, as theoretically predicted. Now, the big news is that the evolution of the EBL over the past 5 billion years has been measured for the first time. That’s because looking farther out into the Universe corresponds to looking back in time. Thus, the gamma ray attenuation spectrum from farther distant blazars reveals how the EBL looked at earlier eras. This was a multistep process. First, the coauthors compared the Fermi findings to intensity of X-rays from the same blazars measured by X-ray satellites Chandra, Swift, Rossi X-ray Timing Explorer, and XMM/Newton and lower-energy radiation measured by other spacecraft and ground-based observatories. From these measurements, Dominguez and collaborators were able to calculate the blazars’ original emitted, unattenuated gamma-ray brightnesses at different energies. The coauthors then compared those calculations of unattenuated gamma-ray flux at different energies with direct measurements from special ground-based telescopes of the actual gamma-ray flux received at Earth from those same blazars. When a high-energy gamma ray from a blazar strikes air molecules in the upper regions of Earth’s atmosphere, it produces a cascade of charged subatomic particles. This cascade of particles travels faster than the speed of light in air, which is slower than the speed of light in a vacuum. This causes a visual analogue to a “sonic boom”: bursts of a special light called Čerenkov radiation. This Čerenkov radiation was detected by imaging atmospheric Čerenkov telescopes (IACTs), such as HESS (High Energy Stereoscopic System) in Namibia, MAGIC (Major Atmospheric Gamma Imaging Čerenkov) in the Canary Islands, and VERITAS (Very Energetic Radiation Imaging Telescope Array Systems) in Arizona. Comparing the calculations of the unattenuated gamma rays to actual measurements of the attenuation of gamma rays and X-rays from blazars at different distances allowed Dominquez and colleagues to quantify the evolution of the EBL, that is, to measure how the EBL changed over time as the Universe aged, out to about 5 billion years ago, corresponding to a redshift of about z = 0.5. “Five billion years ago is the maximum distance we are able to probe with our current technology”, Domínguez said. “Sure, there are blazars farther away, but we are not able to detect them because the high-energy gamma rays they are emitting are too attenuated by EBL when they get to us, so weakened that our instruments are not sensitive enough to detect them”. This measurement is the first statistically significant detection of the so-called “Cosmic Gamma Ray Horizon” as a function of gamma-ray energy. The Cosmic Gamma Ray Horizon is defined as the distance at which roughly one-third or, more precisely, 1/e, that is, 1/2.718 where “e” is the base of the natural logarithms, of the gamma rays of a particular energy have been attenuated. This latest result confirms that the kinds of galaxies observed today are responsible for most of the EBL over all time. Moreover, it sets limits on possible contributions from many galaxies too faint to have been included in the galaxy surveys, or on possible contributions from hypothetical additional sources, such as the decay of hypothetical unknown elementary particles.

UCR: Astronomers Measure the Elusive Extragalactic Background Light
arXiv: Detection of the cosmic γ-ray horizon from multiwavelength observations of blazars